From known amino acids not all have identical value for an organism. Among them there are amino acids which can be replaced by others or synthesized in an organism from other amino acids; along with it there are also irreplaceable amino acids in the absence of which or even the proteinaceous exchange in an organism is broken by one of them.
Trypsin is very active in the alkaline environment. Its action proceeds and in the sour environment, but activity falls. Trypsin affects proteins and splits them to amino acids; it also splits the peptones and albumoza formed in a stomach to amino acids.
For the person important intake of full-fledged proteins as from them the organism can freely synthesize the specific proteins. However full-fledged protein can be replaced by two or three defective squirrels who, supplementing each other, give in the sum all necessary amino acids. Therefore, it is necessary for normal activity of an organism that the food contained full-fledged squirrels or a set of defective proteins, according to the amino-acid contents equivalent to full-fledged proteins.
The usual mixed food contains various squirrels who in the sum provide need of an organism for amino acids. It is important not only the biological value of the proteins arriving with food, but also their quantity. At insufficient amount of proteins the normal growth of an organism stops or late as needs for protein do not become covered because of its insufficient receipt.
The food gruel which came to a duodenum is exposed to further digestion. Here on food gruel juice of intestinal glands with which the mucous membrane of a gut, and also juice of a pancreas and bile is covered streams. Under the influence of this juice feedstuffs - proteins, fats and carbohydrates - are exposed to further splitting and are led up to such state when can be soaked up in blood and a lymph.
The majority of proteins is dissolved in water. Molecules of proteins owing to their big sizes almost do not pass through a time of animal or vegetable membranes. When heating water solutions of proteins turn. There are proteins (for example, gelatin which are dissolved in water only when heating.
At hydrolysis of proteins in sour water solution receive only and - amino acids. Hydrolysis of proteid gives except and substances of not proteinaceous nature (carbohydrates, nucleinic acids, etc.); it compounds of albumens with not proteinaceous.
At compound of two or several amino acids more difficult connection - polypeptide is formed. Polypeptides, connecting, form even more complex and large particles and as a result - a difficult molecule of protein.
Fosfoproteida contain molecules of phosphoric acid, in the form of ester at hydroxyl group of an of a serin. Treats them — the protein containing in an egg yolk, protein of milk casein.
Proteins not always contain all amino acids: one proteins contain bigger amount of amino acids necessary for an organism, in others - insignificant. Different proteins contain various amino acids and in different ratios.